Resources I've used in researching tannins:

Books:

Haslam E. (1989) - Plant polyphenols. Cambridge University Press, Cambridge, UK.

Haslam, E. (1998) - Practical polyphenolics: From structure to molecular recognition & physiological action.  Cambridge University Press, Cambridge, UK.

Hemingway R.W. and Karchesy J.J. eds. (1989) Chemistry and significance of condensed tannins. Plenum Press, New York.

Hemingway, R.W. ed. (1991) Plant Polyphenols: Synthesis, Properties, Significance.  Proceedings of the

Larrouse encyclopedia of wine; Larrouse, New York, 1994.

Second North American Tannin Conference on Plant Polyphenols held in Houghton, Michigan, June 17-21, 1991.  Plenum Press.

Waterman, Peter G., Simon Mole (1994) Analysis of phenolic plant metabolites. Oxford Blackwell Scientific Publications, Boston.

Salunkhe, D.K., J. K. Chavan, and S. S. Kadam, Dietary tannins: consequences and remedies, CRC Press Inc., 1989.

Singleton, Vernon L., "Naturally occurring food toxicants: phenolic substances of plant origin common in foods," Advances in Food Research, vol. 27, p. 149-242.

Balch, James F. and Phyllis A, Balch Prescription for Nutritional Healing, Avery Press, Garden City Park, N.Y., 1997.

Articles:

Butler, Larry G. (1992) -  Antinutritional effects of condensed and hydrolyzable tannins. Plant Polyphenols, Plenum Press, New York. Page 693.

Agricultural Communication Service, Purdue University.  Researcher figures out how tannins block nutrition.  September 23, 1997

Internet resources:

PhytochemDB, by Stephen M. Beckstrom and James A. Duke

Tannins: fascinating but sometimes dangerous molecules, Tannin Home Page at Cornell University

Tannin and Migraine Website Home